2. Add Two Numbers

ou are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8

/**
* Definition for singly-linked list.
* public class ListNode {
*     int val;
*     ListNode next;
*     ListNode(int x) { val = x; }
* }
*/
public class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
int carry = 0;
ListNode dummy = new ListNode(0);
ListNode cur = dummy;
while (l1 != null || l2 != null) {
int a = 0;
int b = 0;
if (l1 != null) {
a = l1.val;
l1 = l1.next;
}
if (l2 != null) {
b = l2.val;
l2 = l2.next;
}
cur.next = new ListNode((a + b + carry) % 10);
carry = (a + b + carry) / 10;
cur = cur.next;
}
if (carry != 0)
cur.next = new ListNode(carry);
return dummy.next;
}
}